The only thing I miss is an "export to file" / "import from file" button thus I can take an installed package list from my house to my workplace and to other OS installs.
Did you try a right click on the tree(as in the attached image)?
OMG
I don't remember if I did it, though the menu translation for "Checked" to spanish is ... "tricky". It should say "Marcado" (marked) or "Seleccionado" (selected) instead of "Comprobado" (checked, ascertain, tested, proved, make sure, check up on, test out).
Beside that, it works for me.
Thank you very much.
P/S: I would add the option to load and save the installed ones. You know I'm a lazy guy and nowadays I don't trust in my eyes nor in my accuracy with the mouse